Japanese Patent Laid-open No. 2001-505014 discloses a measuring device for the interface of a transmission link with full duplex transmission in a two-wire common frequency operation, wherein an interface module is on the one hand connected to said interface via a hybrid circuit and a transformer, and a line termination or a network termination is connected thereto as a test object on the other hand, said measuring device including a means for evaluating the arrangement of the hybrid circuit, the transformer and the line or the network termination, the input of said means being connected to transmission outputs of the interface module via a high-impedance differential amplifier and the output thereof being connected to an input of a subtracter via a further high-impedance differential amplifier, a further input of the subtracter being connected to the interface via an additional high-impedance differential amplifier, the output of the subtracter communicates with a measuring system, a differentiator followed by a comparator being connected to the output of the subtracter, and a jitter measuring device as the measuring system being post-connected to the comparator.
Japanese Patent Laid-open No. 2001-505014